Aripiprazole, as reported in the literature, can exist in multiple crystal forms. For example, PCT publication WO 03/026659 describes at least nine crystal forms, including an hydrate and anhydrous forms, such as Type-I and Type-II. According to WO 03/026659, the procedures disclosed in Proceedings of the 4th Japanese-Korean Symposium on Separation Technology (Oct. 6-8, 1996) yield significantly hydroscopic crystalline forms. The procedures disclosed in the Proceedings yield Type-I crystals of aripiprazole anhydride, prepared by recrystallizing from an ethanol solution of aripiprazole, or by heating aripiprazole hydrate at 80° C. The same Proceedings disclose that Type-II crystals of aripiprazole anhydride can be prepared by heating Type-I crystals of aripiprazole anhydride at 130° C. to 140° C. for 15 hours. In addition to Type-I and Type-II crystals, several additional anhydrous crystal forms are known. PCT publication WO 03/026659 discloses anhydride crystals Form B, C, D, E, F, or G and a hydrate form denominated Form A.
As reported in WO 03/026659, the multiple polymorphs may interconvert from one to the other. For instance, WO 03/026659 discloses that if the anhydrous form is exposed to moisture, then it may take on water and convert into a hydrous form. As stated in WO 03/026659, this presents several disadvantages, for instance the compound may be less bioavailable and less soluble. The hygroscopicity of aripiprazole crystals makes them difficult to handle since costly and burdensome measures must be taken to ensure that the crystals are not exposed to moisture during process and formulation. Despite these concerns, WO 03/026659 discloses a wet granulation process for preparing pharmaceutical compositions using aripiprazole anhydride and various carriers.
WO 03/026659 discloses the wet granulation of conventional aripiprazole anhydride crystals or anhydride Forms B, C, D, E, F, or G, drying the granules at 70° C. to 100° C. and sizing the granules, followed by drying the granules for a second time at a temperature of 70° C. to 100° C.
Other novel crystal aripiprazole forms are disclosed in PCT publication WO 05/058835. These other forms include Form I, II, VII, VIII, X, XI, XII, XIV, XIX, and XX.
Polymorphic transformations may be undesirable during pharmaceutical composition preparation or formulation. However, hydration or manipulation may induce unwanted polymorphic transformations. Also, the process during manufacture may introduce some aripiprazole polymorphs in pharmaceutical tablets other than the original starting material. The aripiprazole polymorphs may be unwanted polymorphs, which may reduce the bioavailability of the drug. Therefore, it would be desirable to develop methods for preparing aripiprazole formulations in which there is no potential of hydration and/or possible polymorphic interconversions.